The standards with high peak-to-average power ratio, such as WiFi, WiMAX, and LTE, require high output power while maintaining high efficiency at back-off. CMOS (complementary metal-oxide semiconductor) processes are well known for their large-scale integration and low cost. They are well suited for digital design, but do not yet achieve a high power and efficient implementation of a radio frequency (RF) power amplifier, due to low device breakdown voltage and passive components in the CMOS process.
Recently, transformer combining has been proposed for producing a higher output power amplifier. While improvements at peak power have been realized with power amplifiers that use transformer combining, efficient power output at back-off power levels remains elusive.
Thus, there is a continuing need for a solution that overcomes the shortcomings of the prior art.